OVER 60-PLUS YEARS I’ve trained many divers, written training packages and 14 books on decompression and diving. So I thought I knew a thing or two about diving, but immersion pulmonary oedema (IPO) was a new one on me.
IPO signifies fluid build-up in the lungs. This leads to shortness of breath, coughing and reduced gas-exchange, which in turn lowers oxygen levels and increases the chance of loss of consciousness, cardiac arrest and death. It is drowning from the inside.
The condition can affect surface-swimmers but can also occur during a dive. I reckon few divers currently recognise IPO as a diving-related topic, but we need to understand as much as there is to know about it, and take precautions to minimise the risks.
The medical profession has no clear idea of the causes of IPO, because fatal cases are often mistaken for drowning. The lungs are waterlogged and heavy either way. Most of what we do know about IPO comes from survivors, some of whom have had recurrent episodes.
IPO is said to be a rare condition, but how can we know this, if some instances are identified simply as drowning?
A colour-changing ‘pee-stick’ can help divers to ensure that they’re neither dehydrated or over-hydrated.
In 2016 Dr Richard Moon, medical director of a US hyperbaric centre, stated that: “During immersion in water, particularly cold water, some people have an exaggerated degree of the normal redistribution of blood from the extremities to the chest area, causing increased pressure in the blood vessels of the lungs, and leakage of fluid into the lungs.”
If swimmers over-hydrate themselves, it seems, hydrostatic pressure can force fluid from their circulatory system through the alveoli walls into the lung air-space. This process could be exacerbated by working hard under water and so breathing harder.
Dr Peter Wilmshurst put the case strongly when addressing last year’s BSAC conference: “IPO is a life-threatening condition and may be the commonest cause of death during diving.”
He and others had published the study Cold-Induced Pulmonary Oedema in Scuba Divers and Swimmers and Subsequent Development of Hypertension in the Lancet in 1989.
For the first time IPO-related deaths were reported in that year’s BSAC Diving Incidents Report, with two cases from overseas plus a further 13 incidents in which IPO was a suspected factor.
So what can we do about this vaguely defined threat? Be aware that certain behaviours increase the risk.
If you have a heart condition or hypertension (high blood pressure), get an examination and advice from a hyperbaric doctor (not a GP) before diving again.
You can lose a lot of body heat even in “warm” water, depending on the length of a dive. If you feel cold, you are cold. Cold water cause blood-vessels to constrict, so wear enough thermal protection.